Influence of network structure on the degradation of poly(ether)amine-cured epoxy resins by inorganic acid

In this paper, we investigate the case of bisphenol-type epoxy crosslinked with poly(ether)amine, immersed in sulfuric acid at elevated temperature. The results show that very high equilibrium mass-change (up to 40%) is observed, and that amine protonation is largely responsible for this behavior. When the acid solution concentration is 5mass% or higher, alcohol dehydration and aromatic ether cleavage reactions occur by excess acid (after amine protonation). A mechanistic degradation model is proposed, which requires no empirical parameters and accounts for polymer network structure differences. The model is supported by calculating the theoretical crosslink density using gravimetric data of penetrated acid at equilibrium.